1624. SARS-CoV-2 Maternal Vaccination Induces More Efficient Placental Antibody Transfer to Newborns than SARS-CoV-2 Infection During Pregnancy

Abstract Background Passive immunization via maternal antibodies (Ab) is a key mechanism for infant protection in early life. This study analyzed the landscape of passive immunization induced by SARS-CoV-2 infection and/or vaccination by comparing the magnitude and durability of the transferred Ab. Methods Prospective multicenter observational cohort study of SARS-CoV2-infected and/or vaccinated pregnant women and their infants. We collected maternal and cord blood samples at delivery and neonatal/infant samples at delivery, and at 1, 2, 6 and 12 months (mo) of age. RBD and Spike IgG Ab titers were measured by ELISA. Results 215 mothers (infected=106, vaccinated=67, infected and vaccinated=42) and 174 infants (n=87, n=54, n=33, respectively) were enrolled. At birth RBD Ab titers median [IQR] of infants from vaccinated mothers [4.28 (3.48-4.80)] log10 ng/ml and from infected and vaccinated mothers [4.61 (4.27-4.93)] log10 ng/ml were higher than those from infected mothers [2.20 (0.10-3.30)] log10 ng/ml, p< 0.001. These differences were observed until 6 mo of age, when only 1/13 (7.7%) infant from infected mothers had detectable maternal Ab compared to 14/15 (93.3%) and 8/8 (100%) from the vaccinated, and infected and vaccinated groups, respectively. At 12 mo none of the infants born to infected mothers had detectable maternal Ab, while in the vaccinated group (n=11), 3 (27.3%) had persistent Ab, and 4 (36.4%) suspected infection. At 12 mo in the infected and vaccinated group (n=6) 3 had no Ab, and 3 had suspected infection. The median [IQR] placental Ab transfer ratio was higher in the vaccinated only group (2.94 [1.34-3.74]) than the infected only group (1.19 [0.33-2.52]) p< 0.01. Linear regression analyses demonstrated that the mean RBD Ab transfer ratio for infants from vaccinated vs infected women was 1.76 (95% CI=1.07-2.88, p=0.025) higher after adjusting for trimester of infection or vaccination. Similar results were observed with Spike Ab. Demographic and clinical characteristics of the study population m; median. IQR; interquartile range. N/A; not applicable. Figure 1. Comparison of RBD antibody titers in infected, vaccinated and infected and vaccinated groups at the time of delivery (from maternal blood, cord blood and neonatal blood) and at months 1, 2, 6 and 12 from neonatal/infant blood. Figure 2. Correlation between maternal and neonatal RBD antibody titers in groups of infected, vaccinated and infected and vaccinated mothers. These correlations also represent the values of the antibody transfer ratios across the placenta. While the bisector (red line) represents the values for a transfer ratio (TR) = 1, all values above it would correspond with TR>1 and those below with TR < 1. Green dots represent the infected group, the blue dots the vaccinated group, and the orange dots the infected and vaccinated group. Conclusion Infants from vaccinated mothers demonstrated maternal Ab up to 6 mo with higher titers than infants born from infected mothers. Antibodies generated by vaccination were transferred more efficiently than those generated by infection regardless of the trimester in which occurred. Disclosures Asuncion Mejias, MD, PhD, MsCS, Astra-Zeneca: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant Octavio Ramilo, MD, AstraZeneca: Honoraria|Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria

Session: 151.Maternal-Child Infections Friday, October 13, 2023: 12:15 PM Background.Passive immunization via maternal antibodies (Ab) is a key mechanism for infant protection in early life.This study analyzed the landscape of passive immunization induced by SARS-CoV-2 infection and/or vaccination by comparing the magnitude and durability of the transferred Ab.
Methods.Prospective multicenter observational cohort study of SARS-CoV2-infected and/or vaccinated pregnant women and their infants.We collected maternal and cord blood samples at delivery and neonatal/infant samples at delivery, and at 1, 2, 6 and 12 months (mo) of age.RBD and Spike IgG Ab titers were measured by ELISA.
Demographic and clinical characteristics of the study population m; median.IQR; interquartile range.N/A; not applicable.

Figure 1 .
Figure 1.Comparison of RBD antibody titers in infected, vaccinated and infected and vaccinated groups at the time of delivery (from maternal blood, cord blood and neonatal blood) and at months 1, 2, 6 and 12 from neonatal/infant blood.

Figure 2 .
Figure 2. Correlation between maternal and neonatal RBD antibody titers in groups of infected, vaccinated and infected and vaccinated mothers.These correlations also represent the values of the antibody transfer ratios across the placenta.While the bisector (red line) represents the values for a transfer ratio (TR) = 1, all values above it would correspond with TR>1 and those below with TR < 1. Green dots represent the infected group, the blue dots the vaccinated group, and the orange dots the infected and vaccinated group.Conclusion.Infants from vaccinated mothers demonstrated maternal Ab up to 6 mo with higher titers than infants born from infected mothers.Antibodies generated by vaccination were transferred more efficiently than those generated by infection regardless of the trimester in which occurred.Disclosures.Asuncion Mejias, MD, PhD, MsCS, Astra-Zeneca: Advisor/ Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant| Sanofi-Pasteur: Advisor/Consultant Octavio Ramilo, MD, AstraZeneca: Honoraria| Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria